bug#23410: 25.1.50; M-s . C-g doesn't quit isearch gracefully

[Chunyang Xu]

To reproduce:

emacs -Q
M-s . C-g

then 'Isearch' remains in mode-line until next command and
'Wrong type argument: arrayp, nil' is displayed in echo area.
After one M-x toggle-debug-on-error, the following is
displayed in *Backtrace* buffer:

Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
  isearch--set-state(nil)
  isearch-pop-state()
  isearch-abort()
  funcall-interactively(isearch-abort)
  call-interactively(isearch-abort nil nil)
  command-execute(isearch-abort)


It should happen whenever the initial input is empty (saying 'No symbol
at point') and type a C-g immediately.


In GNU Emacs 25.1.50.1 (x86_64-apple-darwin15.4.0, NS appkit-1404.46 Version 
10.11.4 (Build 15E65))
 of 2016-04-25 built on MBA.local
Repository revision: 12846626bfae795a173fdedf2850dfbd24065534
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
 'configure --with-modules'

Configured features:
JPEG RSVG IMAGEMAGICK NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS
NS MODULES

Important settings:
  value of $LANG: en_CN.UTF-8
  locale-coding-system: utf-8-unix